blk-wbt: make sure throttle is enabled properly

hulk inclusion
category: bugfix
bugzilla: 109296
CVE: NA
---------------------------

After commit a7905043 ("blk-rq-qos: refactor out common elements of
blk-wbt"), if throttle was disabled by wbt_disable_default(), we could
not enable again, fix this by set enable_state back to
WBT_STATE_ON_DEFAULT.

Fixes: a7905043 ("blk-rq-qos: refactor out common elements of blk-wbt")
Signed-off-by: NZhang Yi <yi.zhang@huawei.com>
Reviewed-by: NYang Erkun <yangerkun@huawei.com>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

block/blk-wbt.c

@@ -709,9 +709,13 @@ void wbt_set_write_cache(struct request_queue *q, bool write_cache_on)
 void wbt_enable_default(struct request_queue *q)
 {
 	struct rq_qos *rqos = wbt_rq_qos(q);
+
 	/* Throttling already enabled? */
-	if (rqos)
+	if (rqos) {
+		if (RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT)
+			RQWB(rqos)->enable_state = WBT_STATE_ON_DEFAULT;
 		return;
+	}
 
 	/* Queue not registered? Maybe shutting down... */
 	if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))